Economic stones have special uses as ore, fuel, flux, plaster, or other uses like making special items. In technical terms, an economic stone is any stone which can be used as a reagent in any form of reaction. Obsidian is an exception, having been made an economic stone even though it is not used in any reaction - its specialty is that it is sharp enough to be used to craft swords.

You can use the z : Stone menu to restrict or un-restrict their use in the production of items and buildings. If you want to use an economic stone for something other than its listed uses, the stone must be green in that menu. This is critical when making a native aluminumstatue, or preventing your masons from making furniture out of all your flux stone.

The z-Status: Stone menu will also show what each stone can be used for -- useful when you are wondering what to do with a pile of tetrahedrite.

This is a list of non-ore stones only; see ore, or the article on that specific material, for more information.